S-Space College of Engineering/Engineering Practice School (공과대학/대학원) Dept. of Mechanical Aerospace Engineering (기계항공공학부) Theses (Ph.D. / Sc.D._기계항공공학부)
Tungsten surface micro structuring technology using laser beam and electrochemical machining
레이저 빔 및 전기화학 복합 가공을 이용한 텅스텐 표면의 마이크로 스트럭쳐링 기술
- 공과대학 기계항공공학부
- Issue Date
- 서울대학교 대학원
- 학위논문 (박사)-- 서울대학교 대학원 : 기계항공공학부, 2016. 8. 주종남.
- In this dissertation, surface structuring to implement various functions was carried out by using hybrid process composed to laser beam machining and electrochemical etching. The suggested method fabricated tungsten easily which had varied applications, and achieved high productivity with fast machining speed, improved surface quality and low cost process, and thus it resolved problems of previous researches to texture tungsten. As using laser beam machining in first step, various shapes of tungsten micro patterning were pre-textured in short time. Generated recast layer and burr were formed on the original core shape that was pre-determined by laser scanning path, and thus degree of precision was low. For this reason, electrochemical etching to improve surface quality was carried out to dissolute recast layer into NaOH electrolyte, and thus pre-defined original micro pattern was revealed.
In this research, guide lines to texture tungsten surface for micro channel and pin were suggested by using new micro structuring method. As combining varied laser scanning path array, fabricated shapes of structures were analyzed, and the resulted tendencies with different laser parameter were studied. Moreover, the solutions to texture vertical micro channel with over 90 °angles of slope and anisotropic angles were introduced by changing laser scanning direction and tilting procedure. The surface analysis of textured structure was achieved as control electrochemical etching time, and the etching conditions were chosen to eliminate recast layer efficiently. EDS analysis was also implemented finally, and thus the principle of the suggested micro hybrid structuring process was verified.
The textured tungsten micro channel was applied to lock each other mechanically, and directional locking force was also measured. The textured tungsten micro pin was used as micro needle for delivering drug, and thus various application areas using newly introduced hybrid structuring process were suggested.